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  • Java: Cleaning up what causes a connection reset

    - by Zombies
    There seems to be some confusion as well contradicting statements on various SO answers: http://stackoverflow.com/questions/585599/whats-causing-my-java-net-socketexception-connection-reset . You can see here that the accepted answer states that the connection was closed by other side. But this is not true, closing a connection doesn't cause a connection reset. It is cauesed by "an underlying TCP/IP error." What I want to know is if a SocketException: Connection reset means really besides "unerlying TCP/IP Error." What really causes this? As I doubt it has anything to do with the connection being closed (since closing a connection isn't an exception worthy flag, and reading from a closed connection is, but that isn't an "underlying TCP/IP error." My hypothesis is this Connection reset is caused from a server's failure to acknowledge an ACK packet (either wholly or just improperly as per TCP/IP). And that a SocketTimeoutException is generated only when no data is generated to be read (since this is thrown during a read after a certain duration, and read is waiting for data, but is not concerned with ACK packets). In other words, read() throws SocketTimeoutException if it didn't read any bytes of actual data (DATA LAYER) in its allotted time.

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  • Java File IO Compendium

    - by Warren Taylor
    I've worked in and around Java for nigh on a decade, but have managed to ever avoid doing serious work with files. Mostly I've written database driven applications, but occasionally, even those require some file io. Since I do it so rarely, I end up googling around for quite some time to figure out the exact incantation that Java requires to read a file into a byte[], char[], String or whatever I need at the time. For a 'once and for all' list, I'd like to see all of the usual ways to get data from a file into Java, or vice versa. There will be a fair bit of overlap, but the point is to define all of the subtle different variants that are out there. For example: Read/Write a text file from/to a single String. Read a text file line by line. Read/Write a binary file from/to a single byte[]. Read a binary file into a byte[] of size x, one chunk at a time. The goal is to show concise ways to do each of these. Samples do not need to handle missing files or other errors, as that is generally domain specific. Feel free to suggest more IO tasks that are somewhat common and I have neglected to mention.

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  • tmpfile and gzip combination problem

    - by Vojtech R.
    I have problem with this code: file = tempfile.TemporaryFile(mode='wrb') file.write(base64.b64decode(data)) file.flush() os.fsync(file) # file.seek(0) f = gzip.GzipFile(mode='rb', fileobj=file) print f.read() I dont know why it doesn't print out anything. If I uncomment file.seek then error occurs: File "/usr/lib/python2.5/gzip.py", line 263, in _read self._read_gzip_header() File "/usr/lib/python2.5/gzip.py", line 162, in _read_gzip_header magic = self.fileobj.read(2) IOError: [Errno 9] Bad file descriptor Just for information this version works fine: x = open("test.gzip", 'wb') x.write(base64.b64decode(data)) x.close() f = gzip.GzipFile('test.gzip', 'rb') print f.read()

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  • Strange Recurrent Excessive I/O Wait

    - by Chris
    I know quite well that I/O wait has been discussed multiple times on this site, but all the other topics seem to cover constant I/O latency, while the I/O problem we need to solve on our server occurs at irregular (short) intervals, but is ever-present with massive spikes of up to 20k ms a-wait and service times of 2 seconds. The disk affected is /dev/sdb (Seagate Barracuda, for details see below). A typical iostat -x output would at times look like this, which is an extreme sample but by no means rare: iostat (Oct 6, 2013) tps rd_sec/s wr_sec/s avgrq-sz avgqu-sz await svctm %util 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 16.00 0.00 156.00 9.75 21.89 288.12 36.00 57.60 5.50 0.00 44.00 8.00 48.79 2194.18 181.82 100.00 2.00 0.00 16.00 8.00 46.49 3397.00 500.00 100.00 4.50 0.00 40.00 8.89 43.73 5581.78 222.22 100.00 14.50 0.00 148.00 10.21 13.76 5909.24 68.97 100.00 1.50 0.00 12.00 8.00 8.57 7150.67 666.67 100.00 0.50 0.00 4.00 8.00 6.31 10168.00 2000.00 100.00 2.00 0.00 16.00 8.00 5.27 11001.00 500.00 100.00 0.50 0.00 4.00 8.00 2.96 17080.00 2000.00 100.00 34.00 0.00 1324.00 9.88 1.32 137.84 4.45 59.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 22.00 44.00 204.00 11.27 0.01 0.27 0.27 0.60 Let me provide you with some more information regarding the hardware. It's a Dell 1950 III box with Debian as OS where uname -a reports the following: Linux xx 2.6.32-5-amd64 #1 SMP Fri Feb 15 15:39:52 UTC 2013 x86_64 GNU/Linux The machine is a dedicated server that hosts an online game without any databases or I/O heavy applications running. The core application consumes about 0.8 of the 8 GBytes RAM, and the average CPU load is relatively low. The game itself, however, reacts rather sensitive towards I/O latency and thus our players experience massive ingame lag, which we would like to address as soon as possible. iostat: avg-cpu: %user %nice %system %iowait %steal %idle 1.77 0.01 1.05 1.59 0.00 95.58 Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn sdb 13.16 25.42 135.12 504701011 2682640656 sda 1.52 0.74 20.63 14644533 409684488 Uptime is: 19:26:26 up 229 days, 17:26, 4 users, load average: 0.36, 0.37, 0.32 Harddisk controller: 01:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS 1078 (rev 04) Harddisks: Array 1, RAID-1, 2x Seagate Cheetah 15K.5 73 GB SAS Array 2, RAID-1, 2x Seagate ST3500620SS Barracuda ES.2 500GB 16MB 7200RPM SAS Partition information from df: Filesystem 1K-blocks Used Available Use% Mounted on /dev/sdb1 480191156 30715200 425083668 7% /home /dev/sda2 7692908 437436 6864692 6% / /dev/sda5 15377820 1398916 13197748 10% /usr /dev/sda6 39159724 19158340 18012140 52% /var Some more data samples generated with iostat -dx sdb 1 (Oct 11, 2013) Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sdb 0.00 15.00 0.00 70.00 0.00 656.00 9.37 4.50 1.83 4.80 33.60 sdb 0.00 0.00 0.00 2.00 0.00 16.00 8.00 12.00 836.00 500.00 100.00 sdb 0.00 0.00 0.00 3.00 0.00 32.00 10.67 9.96 1990.67 333.33 100.00 sdb 0.00 0.00 0.00 4.00 0.00 40.00 10.00 6.96 3075.00 250.00 100.00 sdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.00 0.00 0.00 100.00 sdb 0.00 0.00 0.00 2.00 0.00 16.00 8.00 2.62 4648.00 500.00 100.00 sdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 0.00 100.00 sdb 0.00 0.00 0.00 1.00 0.00 16.00 16.00 1.69 7024.00 1000.00 100.00 sdb 0.00 74.00 0.00 124.00 0.00 1584.00 12.77 1.09 67.94 6.94 86.00 Characteristic charts generated with rrdtool can be found here: iostat plot 1, 24 min interval: http://imageshack.us/photo/my-images/600/yqm3.png/ iostat plot 2, 120 min interval: http://imageshack.us/photo/my-images/407/griw.png/ As we have a rather large cache of 5.5 GBytes, we thought it might be a good idea to test if the I/O wait spikes would perhaps be caused by cache miss events. Therefore, we did a sync and then this to flush the cache and buffers: echo 3 > /proc/sys/vm/drop_caches and directly afterwards the I/O wait and service times virtually went through the roof, and everything on the machine felt like slow motion. During the next few hours the latency recovered and everything was as before - small to medium lags in short, unpredictable intervals. Now my question is: does anybody have any idea what might cause this annoying behaviour? Is it the first indication of the disk array or the raid controller dying, or something that can be easily mended by rebooting? (At the moment we're very reluctant to do this, however, because we're afraid that the disks might not come back up again.) Any help is greatly appreciated. Thanks in advance, Chris. Edited to add: we do see one or two processes go to 'D' state in top, one of which seems to be kjournald rather frequently. If I'm not mistaken, however, this does not indicate the processes causing the latency, but rather those affected by it - correct me if I'm wrong. Does the information about uninterruptibly sleeping processes help us in any way to address the problem? @Andy Shinn requested smartctl data, here it is: smartctl -a -d megaraid,2 /dev/sdb yields: smartctl 5.40 2010-07-12 r3124 [x86_64-unknown-linux-gnu] (local build) Copyright (C) 2002-10 by Bruce Allen, http://smartmontools.sourceforge.net Device: SEAGATE ST3500620SS Version: MS05 Serial number: Device type: disk Transport protocol: SAS Local Time is: Mon Oct 14 20:37:13 2013 CEST Device supports SMART and is Enabled Temperature Warning Disabled or Not Supported SMART Health Status: OK Current Drive Temperature: 20 C Drive Trip Temperature: 68 C Elements in grown defect list: 0 Vendor (Seagate) cache information Blocks sent to initiator = 1236631092 Blocks received from initiator = 1097862364 Blocks read from cache and sent to initiator = 1383620256 Number of read and write commands whose size <= segment size = 531295338 Number of read and write commands whose size > segment size = 51986460 Vendor (Seagate/Hitachi) factory information number of hours powered up = 36556.93 number of minutes until next internal SMART test = 32 Error counter log: Errors Corrected by Total Correction Gigabytes Total ECC rereads/ errors algorithm processed uncorrected fast | delayed rewrites corrected invocations [10^9 bytes] errors read: 509271032 47 0 509271079 509271079 20981.423 0 write: 0 0 0 0 0 5022.039 0 verify: 1870931090 196 0 1870931286 1870931286 100558.708 0 Non-medium error count: 0 SMART Self-test log Num Test Status segment LifeTime LBA_first_err [SK ASC ASQ] Description number (hours) # 1 Background short Completed 16 36538 - [- - -] # 2 Background short Completed 16 36514 - [- - -] # 3 Background short Completed 16 36490 - [- - -] # 4 Background short Completed 16 36466 - [- - -] # 5 Background short Completed 16 36442 - [- - -] # 6 Background long Completed 16 36420 - [- - -] # 7 Background short Completed 16 36394 - [- - -] # 8 Background short Completed 16 36370 - [- - -] # 9 Background long Completed 16 36364 - [- - -] #10 Background short Completed 16 36361 - [- - -] #11 Background long Completed 16 2 - [- - -] #12 Background short Completed 16 0 - [- - -] Long (extended) Self Test duration: 6798 seconds [113.3 minutes] smartctl -a -d megaraid,3 /dev/sdb yields: smartctl 5.40 2010-07-12 r3124 [x86_64-unknown-linux-gnu] (local build) Copyright (C) 2002-10 by Bruce Allen, http://smartmontools.sourceforge.net Device: SEAGATE ST3500620SS Version: MS05 Serial number: Device type: disk Transport protocol: SAS Local Time is: Mon Oct 14 20:37:26 2013 CEST Device supports SMART and is Enabled Temperature Warning Disabled or Not Supported SMART Health Status: OK Current Drive Temperature: 19 C Drive Trip Temperature: 68 C Elements in grown defect list: 0 Vendor (Seagate) cache information Blocks sent to initiator = 288745640 Blocks received from initiator = 1097848399 Blocks read from cache and sent to initiator = 1304149705 Number of read and write commands whose size <= segment size = 527414694 Number of read and write commands whose size > segment size = 51986460 Vendor (Seagate/Hitachi) factory information number of hours powered up = 36596.83 number of minutes until next internal SMART test = 28 Error counter log: Errors Corrected by Total Correction Gigabytes Total ECC rereads/ errors algorithm processed uncorrected fast | delayed rewrites corrected invocations [10^9 bytes] errors read: 610862490 44 0 610862534 610862534 20470.133 0 write: 0 0 0 0 0 5022.480 0 verify: 2861227413 203 0 2861227616 2861227616 100872.443 0 Non-medium error count: 1 SMART Self-test log Num Test Status segment LifeTime LBA_first_err [SK ASC ASQ] Description number (hours) # 1 Background short Completed 16 36580 - [- - -] # 2 Background short Completed 16 36556 - [- - -] # 3 Background short Completed 16 36532 - [- - -] # 4 Background short Completed 16 36508 - [- - -] # 5 Background short Completed 16 36484 - [- - -] # 6 Background long Completed 16 36462 - [- - -] # 7 Background short Completed 16 36436 - [- - -] # 8 Background short Completed 16 36412 - [- - -] # 9 Background long Completed 16 36404 - [- - -] #10 Background short Completed 16 36401 - [- - -] #11 Background long Completed 16 2 - [- - -] #12 Background short Completed 16 0 - [- - -] Long (extended) Self Test duration: 6798 seconds [113.3 minutes]

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  • May the FileInputStream.available foolish me?

    - by Tom Brito
    This FileInputStream.available() javadoc says: Returns an estimate of the number of remaining bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream. The next invocation might be the same thread or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes. In some cases, a non-blocking read (or skip) may appear to be blocked when it is merely slow, for example when reading large files over slow networks. I'm not sure if in this check: if (new FileInputStream(xmlFile).available() == 0) can I rely that empty files will always return zero?

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  • Windows Server 2003 Hacked - Files Being Uploaded

    - by jreedinc
    Blank directories are being created on my Windows Server 2003 virtual server with sub directories that are weird (for example: "88ÿ ÿ ÿÿþþ þþ13þ"). It looks like they are uploading bootlegged DVDs and pirated software. All of my bandwidth and file space is being eaten up. Could this be a shared permissions issue? Where should I look to further investigate this? My security permissions for the directory that is being hit are as followed: Administrators - ALL GRANTED IIS_WPG - Read & Execute, List Folder Contents, Read Internet Guest - DENY SYSTEM - ALL GRANTED Users - Read & Execute, List Folder Contents, Read My Event Viewer is showing many Logon/Logoff with NO IP?

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  • Distributed transactions

    - by javi
    Hello! I've a question regarding distributed transactions. Let's assume I have 3 transaction programs: Transaction A begin a=read(A) b=read(B) c=a+b write(C,c) commit Transaction B begin a=read(A) a=a+1 write(A,a) commit Transaction C begin c=read(C) c=c*2 write(A,c) commit So there are 5 pairs of critical operations: C2-A5, A2-B4, B4-C4, B2-C4, A2-C4. I should ensure integrity and confidentiality, do you have any idea of how to achieve it? Thank you in advance!

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  • Jpeg 2000 and .net

    - by pho3nix
    I working in a activex control using .net for load it in a ie website. I need read a jpeg 2000 file but i don't want use a 3rd party dll because this will cause dependencies or embedding it make my dll very big. Anyone have idea where i can find a class .cs for embedded on my project, i need only read file, no write only read.

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  • Accessing StackExchange API from Emacs

    - by cschol
    I am trying to access the StackExchange API from Emacs' elisp: (require 'url) (require 'json) (defvar url-http-end-of-headers) (defun read-json () (interactive) (with-current-buffer (url-retrieve-synchronously "http://api.stackoverflow.com/0.8/users/2386") (goto-char url-http-end-of-headers) (json-read))) M-x read-json results in the following error: JSON readtable error. Am I missing anything?

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  • method names with fluent interface

    - by deamon
    I have a Permissions class with methods in fluent style like this: somePermissions.setRead(true).setWrite(false).setExecute(true) The question is, whether I should name these methods set{Property} or only {property}. The latter would look like this: somePermissions.read(true).write(false).execute(true) If I look at these methods separately I would expect that read reads something, but on the other hand it is closer to the intention to have something like named paramaters like in Scala: Permission(read=true, write=false, execute=true)

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  • Producer / Consumer - I/O Disk

    - by Pedro Magalhaes
    Hi, I have a compressed file in the disk, that a partitioned in blocks. I read a block from disk decompress it to memory and the read the data. It is possible to create a producer/consumer, one thread that recovers compacted blocks from disk and put in a queue and another thread that decompress and read the data? Will the performance be better? Thanks!

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  • ArgumentOutOfRangeException when reading bytes from stream

    - by user345194
    I'm trying to read the response stream from an HttpWebResponse object. I know the length of the stream (_response.ContentLength) however I keep getting the following exception: Specified argument was out of the range of valid values. Parameter name: size While debugging, I noticed that at the time of the error, the values were as such: length = 15032 //the length of the stream as defined by _response.ContentLength bytesToRead = 7680 //the number of bytes in the stream that still need to be read bytesRead = 7680 //the number of bytes that have been read (offset) body.length = 15032 //the size of the byte[] the stream is being copied to The peculiar thing is that the bytesToRead and bytesRead variables are ALWAYS 7680, regardless of the size of the stream (contained in the length variable). Any ideas? Code: int length = (int)_response.ContentLength; byte[] body = null; if (length 0) { int bytesToRead = length; int bytesRead = 0; try { body = new byte[length]; using (Stream stream = _response.GetResponseStream()) { while (bytesToRead > 0) { // Read may return anything from 0 to length. int n = stream.Read(body, bytesRead, length); // The end of the file is reached. if (n == 0) break; bytesRead += n; bytesToRead -= n; } stream.Close(); } } catch (Exception exception) { throw; } } else { body = new byte[0]; } _responseBody = body;

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  • Writing file from HttpWebRequest periodically vs. after download finishes?

    - by WB3000
    Right now I am using this code to download files (with a Range header). Most of the files are large, and it is running 99% of CPU currently as the file downloads. Is there any way that the file can be written periodically so that it does not remain in RAM constantly? private byte[] GetWebPageContent(string url, long start, long finish) { byte[] result = new byte[finish]; HttpWebRequest request; request = WebRequest.Create(url) as HttpWebRequest; //request.Headers.Add("Range", "bytes=" + start + "-" + finish); request.AddRange((int)start, (int)finish); using (WebResponse response = request.GetResponse()) { return ReadFully(response.GetResponseStream()); } } public static byte[] ReadFully(Stream stream) { byte[] buffer = new byte[32768]; using (MemoryStream ms = new MemoryStream()) { while (true) { int read = stream.Read(buffer, 0, buffer.Length); if (read <= 0) return ms.ToArray(); ms.Write(buffer, 0, read); } } }

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  • Caching in mmap

    - by myahya
    I am using mmap call to read from a very big file using simple pointer arithmetic in C++. The problem is that when I read small chunks of data (in the order of KBs) multiple times, each read take the same amount of time as the previous one. How can I know if the disk is being accessed to fulfill my request or whether the request is being fulfilled from main memory (page cache) in calls after the first one.

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  • How to MakeTable ReadOnly including contents like images

    - by GustlyWind
    I have a table which has two text boxes and a image beside it to click and open a popup. In read-only mode based on condition I am able to make text boxes read-only but images are not becoming read-only.One solution I had is the anchor tag associated with image calls for JavaScript where I can check for a dummy click when it is in read-only mode. The problem here is the function is common and effects everywhere. So is there a way to make the entire table read-only so that no extra workaround needs to done. Edited for code <table> <tr> <td class="lightbg" colspan='4'>&nbsp; Expires:<input type="TEXT" value="" id="element1" name="expireDate" size="10" maxlength="20" class="" onChange="javascript:validateDateEntry('element1',true);;"> Period:<input type="TEXT" value="" id="element2" name="refershDate" size="10" maxlength="20" class="" onChange="javascript:validateDateEntry('element2',true);;"> &nbsp; <a href="javascript:doCalendar('element1');"> <img src="/PWM/images/images_2006/calendarbtn.gif" border="0" alt="Click to select date from calendar" align="absmiddle"> </a> </td> </tr> <tr> <td colspan='4'><b>*</b>Times are in the WFM Server's Time Zone.</td></tr> </table> Thanks

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  • Javascript - how to replace a sub-string?

    - by Jangwenyi
    This is a simple one. I want to replace a sub-string with another sub-string on client-side using Javascript. Original string is 'original READ ONLY' I want to replace the 'READ ONLY' with 'READ WRITE' Any quick answer please? Possibly with a javascript code snippet...

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  • Odd performance with C# Asynchronous server socket

    - by The.Anti.9
    I'm working on a web server in C# and I have it running on Asynchronous socket calls. The weird thing is that for some reason, when you start loading pages, the 3rd request is where the browser won't connect. It just keeps saying "Connecting..." and doesn't ever stop. If I hit stop. and then refresh, it will load again, but if I try another time after that it does the thing where it doesn't load again. And it continues in that cycle. I'm not really sure what is making it do that. The code is kind of hacked together from a couple of examples and some old code I had. Any miscellaneous tips would be helpful as well. Heres my little Listener class that handles everything (pastied here. thought it might be easier to read this way) using System; using System.Collections.Generic; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading; namespace irek.Server { public class Listener { private int port; private Socket server; private Byte[] data = new Byte[2048]; static ManualResetEvent allDone = new ManualResetEvent(false); public Listener(int _port) { port = _port; } public void Run() { server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint iep = new IPEndPoint(IPAddress.Any, port); server.Bind(iep); Console.WriteLine("Server Initialized."); server.Listen(5); Console.WriteLine("Listening..."); while (true) { allDone.Reset(); server.BeginAccept(new AsyncCallback(AcceptCon), server); allDone.WaitOne(); } } private void AcceptCon(IAsyncResult iar) { allDone.Set(); Socket s = (Socket)iar.AsyncState; Socket s2 = s.EndAccept(iar); SocketStateObject state = new SocketStateObject(); state.workSocket = s2; s2.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); } private void Read(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; Socket s = state.workSocket; int read = s.EndReceive(iar); if (read > 0) { state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, read)); if (s.Available > 0) { s.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); return; } } if (state.sb.Length > 1) { string requestString = state.sb.ToString(); // HANDLE REQUEST HERE // Temporary response string resp = "<h1>It Works!</h1>"; string head = "HTTP/1.1 200 OK\r\nContent-Type: text/html;\r\nServer: irek\r\nContent-Length:"+resp.Length+"\r\n\r\n"; byte[] answer = Encoding.ASCII.GetBytes(head+resp); // end temp. state.workSocket.BeginSend(answer, 0, answer.Length, SocketFlags.None, new AsyncCallback(Send), state.workSocket); } } catch (Exception) { return; } } private void Send(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; int sent = state.workSocket.EndSend(iar); state.workSocket.Shutdown(SocketShutdown.Both); state.workSocket.Close(); } catch (Exception) { } return; } } } And my SocketStateObject: public class SocketStateObject { public Socket workSocket = null; public const int BUFFER_SIZE = 1024; public byte[] buffer = new byte[BUFFER_SIZE]; public StringBuilder sb = new StringBuilder(); }

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  • How large a role does subjectiveness play in programming?

    - by Bob
    I often read about the importance of readability and maintainability. Or, I read very strong opinions about which syntax features are bad or good. Or discussions about the values of certain paradigms, like OOP. Aside from that, this same question floats about in my mind whenever I read debates on SO or Meta about subjective questions. Or read questions about best practices and sometimes find myself or others disagreeing. What role does subjectiveness play within the programming realm? Sometimes I think it plays a large role. Software developers are engineers in a way, but also people. A large part of programming is dealing with code that's human readable. This is very different from Math or Physics or other disciplines with very exact and structured rules. Here the exact structure and rules are largely up in the air, changeable on a whim, and hence the amount of languages in existence. And one person may find one language very readable, and another person may find their own language the most comforting. The same with practices. One person may not like certain accepted practices. I myself find splitting classes into different files very unreadable, for instance. But, I can't say rules haven't helped in general. Certain practices have and do make life easier. And new languages have given rise to syntax and structure that make life easier. There's certainly been a progression towards code that is easier to read and maintain even given a largely diverse group of people. So maybe these things aren't as subjective as I thought. It reminds me, in a way, of UI design. Certainly it's subjective, but then there's an entire discipline involved in crafting good UI and it tends to work. Is there something non-subjective about the ideas behind maintainability, readability, and other best practices? Is there something tangible to grasp when one develops a new language or thinks of new practices?

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  • What are the permissions I need?

    - by Eric
    My folder at: /usr/local/www/.ext_env_vars has a bunch of files in it that my app needs to read. The user is 'webapp' So, I changed the perms like so: chmod -R 400 .ext_env_vars chown -R webapp.webapp .ext_env_vars The application can't read these. However, when I chmod 777, they are read by the app. So, it isn't that I have a path problem. Seems to be permissions only. So, what would I have to do to the permissions to make webapp be able to read those files in the .ext_env_vars folder? Thanks Eric

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  • Java multiple connections downloading file

    - by weulerjunior
    Hello friends, I was wanting to add multiple connections in the code below to be able to download files faster. Could someone help me? Thanks in advance. public void run() { RandomAccessFile file = null; InputStream stream = null; try { // Open connection to URL. HttpURLConnection connection = (HttpURLConnection) url.openConnection(); // Specify what portion of file to download. connection.setRequestProperty("Range", "bytes=" + downloaded + "-"); // Connect to server. connection.connect(); // Make sure response code is in the 200 range. if (connection.getResponseCode() / 100 != 2) { error(); } // Check for valid content length. int contentLength = connection.getContentLength(); if (contentLength < 1) { error(); } /* Set the size for this download if it hasn't been already set. */ if (size == -1) { size = contentLength; stateChanged(); } // Open file and seek to the end of it. file = new RandomAccessFile("C:\\"+getFileName(url), "rw"); file.seek(downloaded); stream = connection.getInputStream(); while (status == DOWNLOADING) { /* Size buffer according to how much of the file is left to download. */ byte buffer[]; if (size - downloaded > MAX_BUFFER_SIZE) { buffer = new byte[MAX_BUFFER_SIZE]; } else { buffer = new byte[size - downloaded]; } // Read from server into buffer. int read = stream.read(buffer); if (read == -1) { break; } // Write buffer to file. file.write(buffer, 0, read); downloaded += read; stateChanged(); } /* Change status to complete if this point was reached because downloading has finished. */ if (status == DOWNLOADING) { status = COMPLETE; stateChanged(); } } catch (Exception e) { error(); } finally { // Close file. if (file != null) { try { file.close(); } catch (Exception e) { } } // Close connection to server. if (stream != null) { try { stream.close(); } catch (Exception e) { } } } }

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  • How to get image height and width using java?

    - by Dick Song
    Is there any other way beside using imageIO.read to get image height and width? Because I encounter some issue that will lockup the thread. at com.sun.medialib.codec.jpeg.Decoder.njpeg_decode(Native Method) at com.sun.medialib.codec.jpeg.Decoder.decode(Decoder.java:87) at com.sun.media.imageioimpl.plugins.jpeg.CLibJPEGImageReader.decode(CLibJPEGImageReader.java:73) - locked <0xd96fb668> (a com.sun.media.imageioimpl.plugins.jpeg.CLibJPEGImageReader) at com.sun.media.imageioimpl.plugins.clib.CLibImageReader.getImage(CLibImageReader.java:320) - locked <0xd96fb668> (a com.sun.media.imageioimpl.plugins.jpeg.CLibJPEGImageReader) at com.sun.media.imageioimpl.plugins.clib.CLibImageReader.read(CLibImageReader.java:384) - locked <0xd96fb668> (a com.sun.media.imageioimpl.plugins.jpeg.CLibJPEGImageReader) at javax.imageio.ImageIO.read(ImageIO.java:1400) at javax.imageio.ImageIO.read(ImageIO.java:1322) This error only occurs on sun app server I suspect that it is a sun bug

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  • How to program critical section for reader-writer systems?

    - by Srinivas Nayak
    Hi, Lets say, I have a reader-writer system where reader and writer are concurrently running. 'a' and 'b' are two shared variables, which are related to each other, so modification to them needs to be an atomic operation. A reader-writer system can be of the following types: rr ww r-w r-ww rr-w rr-ww where [ r : single reader rr: multiple reader w : single writer ww: multiple writer ] Now, We can have a read method for a reader and a write method for a writer as follows. I have written them system type wise. rr read_method { read a; read b; } ww write_method { lock(m); write a; write b; unlock(m); } r-w r-ww rr-w rr-ww read_method { lock(m); read a; read b; unlock(m); } write_method { lock(m); write a; write b; unlock(m); } For multiple reader system, shared variable access doesn't need to be atomic. For multiple writer system, shared variable access need to be atomic, so locked with 'm'. But, for system types 3 to 6, is my read_method and write_method correct? How can I improve? Sincerely, Srinivas Nayak

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  • Why do i get E_ACCESSDENIED when reading public shortcuts through Shell32?

    - by corvuscorax
    I'm trying to read the targets of all desktop shortcuts in a C# 4 application. The shortcuts on a windows desktop can come from more that one location, depending on whether the shortcut is created for all users or just the current user. In this specific case I'm trying to read a shortcut from the public desktop, e.g. from C:\Users\Public\Desktop\shortcut.lnk. The code is like this (path is a string contaning the path to the lnk file): var shell = new Shell32.ShellClass(); var folder = shell.NameSpace(Path.GetDirectoryName(path)); var folderItem = folder.ParseName(Path.GetFileName(path)); if (folderItem != null) { var link = (Shell32.ShellLinkObject)folderItem.GetLink; The last line throws an System.UnauthorizedAccessException, indicating that it's not allowed to read the shortcut file's contents. I have tried on shortcut files on the user's private desktop (c:\Users\username\Desktop) and that works fine. So, my questions are: (1) why is my application not allowed to /read/ the shortcut from code, when I can clearly read the contents as a user? (2) is there a way to get around this? Maybe using a special manifest file for the application? And, by the way, my OS is Windows 7, 64-bit. be well -h-

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  • File not readable exception - pear/Config_Lite

    - by CasperNine
    I have two config files located in: /etc/svnauth and var/www/svnauth I have given read, write access to for both files like shown below chown -R apache:apache /etc/svnauth chmod -R 770 /etc/svnauth chown -R apache:apache /var/www/svnauth chmod -R 770 /var/www/svnauth When I try to read these two files using pear/Config_Lite, /etc/svnauth always fails. I can successfully read the /var/www/svnauth file Any reasons for this? What am I missing here Following is the error message i get: Fatal error: Uncaught exception 'Config_Lite_Exception_Runtime' with message 'file not readable: /etc/svnauth' in /var/www/html/svnmanager/Config/Lite.php:112 Stack trace: #0 /var/www/html/svnmanager/index.php(60): Config_Lite->read('/etc/svnauth') #1 {main} thrown in /var/www/html/svnmanager/Config/Lite.php on line 112

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